MEMS are devices having sub-millimeter-sized micro-mechanical components. Some MEMS have a resonating micro-mechanical structure that oscillates at its natural frequency. Resonator MEMS have been used in switches (U.S. Pat. No. 6,744,338 B2) and tunable capacitor application (U.S. Pat. No. 7,095,295 B1). The resonating micro-mechanical structures in these devices comprises a cantilever that resonates within a relatively large gap of a few thousand Ångstroms to few microns. Such large gap accommodates the large oscillation amplitude of the cantilever, and a relatively large amount of energy is required for causing the cantilever to oscillate within the gap.
In switching applications, a known MEMS device uses the mechanical connection between an electrode or contact associated with a resonating micro-mechanical structure and a switch electrode or contact. In situations where two surfaces scaled in the micrometer ranges come into close proximity, such surfaces may adhere to each other because, at such small scale, electrostatic (and/or Van der Waals) forces become significant producing a problematic phenomena known as stiction. MEMS switches suffer from stiction when the different electrical potentials applied to the electrodes reduces switching reliability.
In quantum mechanics, tunnelling effect (also known as quantum tunnelling) is a nanoscopic phenomenon in which a particle violates the principles of classical mechanics by penetrating a potential barrier or impedance higher than the kinetic energy of the particle. Such tunnelling effect has been used in a known MEMS tunnelling/capacitive sensor (U.S. Pat. No. 6,835,587 B2), which has a cantilevered resonator structure with a gap size of about 3,000 Å.
Scanning tunnelling microscope (STM) is a technique for viewing surfaces at the atomic level. The STM is based on the concept of quantum tunnelling. When a conducting tip is brought very near to a metallic or semi-conducting surface, a bias between the two can allow electrons to tunnel through the vacuum between them. For low voltages, this tunnelling current is a function of the local density of states (LDOS) at the Fermi level, Ef, of the sample. Variations in current as the probe passes over the surface are translated into an image.
Oscillating cantilevers have been used in atomic force microscopy (AFM). In such applications, external laser beam detection systems measure the deflection angle of the cantilever using a feedback mechanism. The relatively large size of the cantilevers allows for the detection of laser beam reflections from probed surfaces. Large cantilevers, however, do not allow for detection of extremely small deflection angles that are necessary for high resolution microscopy. This is because such angles are difficult to measure due to optical limitations associated with diffraction in laser beams.
Accordingly, the prior art MEMS devices have resolution limitations for detecting very small forces, such as, atomic forces and photons. Therefore, there exists a need for a MEMS device that provides higher detection resolution.